Electro-Magnetic Locating
Electro-Magnetic Locating uses a transmitter that transmits an extremely low voltage current onto a conductive material (e.g. a pipe that is steel or polyethylene with tracing wire attached to it). The underground object can then be accurately located and traced with a wand-like receiver that detects the EM fields that have been created around the buried service.
The three main forms of EM locating are:
Conductive Locating – the transmitter is connected directly to a utility line or trace wire. The signal creates a field around the outside of the conductive material. The receiver detects this field and therefore enables you to locate and trace the utility line or trace wire.
Inductive Locating – the signal is applied onto the target line without physically connecting onto the utility material. There are two methods of inductive locating: coupling and standard. Coupling involves clamping around a utility line, whereas standard involves placing the transmitter on the ground above the buried utility line.
Passive Locating – The receiver is used alone to detect any signals that originate from other sources, such as electrical power and broadcast waves.
What are the pitfalls of EM Locating?
Depth reading is only approximate and cannot be used as a digging guide; specific identification of a targeted service in congested areas is very difficult